Until Nov. 8, 2016, historians of American politics shared a rough consensus about the rise of modern American conservatism. It told a respectable tale. By the end of World War II, the story goes, conservatives had become a scattered and obscure remnant, vanquished by the New Deal and the apparent reality that, as the critic Lionel Trilling wrote in 1950, liberalism was “not only the dominant but even the sole intellectual tradition.”

Year Zero was 1955, when William F. Buckley Jr. started National Review, the small-circulation magazine whose aim, Buckley explained, was to “articulate a position on world affairs which a conservative candidate can adhere to without fear of intellectual embarrassment or political surrealism.” Buckley excommunicated the John Birch Society, anti-Semites and supporters of the hyperindividualist Ayn Rand, and his cohort fused the diverse schools of conservative thinking — traditionalist philosophers, militant anti-Communists, libertarian economists — into a coherent ideology, one that eventually came to dominate American politics.

I was one of the historians who helped forge this narrative. My first book, “Before the Storm,” was about the rise of Senator Barry Goldwater, the uncompromising National Review favorite whose refusal to exploit the violent backlash against civil rights, and whose bracingly idealistic devotion to the Constitution as he understood it — he called for Social Security to be made “voluntary” — led to his crushing defeat in the 1964 presidential election. Goldwater’s loss, far from dooming the American right, inspired a new generation of conservative activists to redouble their efforts, paving the way for the Reagan revolution. Educated whites in the prosperous metropolises of the New South sublimated the frenetic, violent anxieties that once marked race relations in their region into more palatable policy concerns about “stable housing values” and “quality local education,” backfooting liberals and transforming conservatives into mainstream champions of a set of positions with enormous appeal to the white American middle class.

These were the factors, many historians concluded, that made America a “center right” nation. For better or for worse, politicians seeking to lead either party faced a new reality. Democrats had to honor the public’s distrust of activist government (as Bill Clinton did with his call for the “end of welfare as we know it”). Republicans, for their part, had to play the Buckley role of denouncing the political surrealism of the paranoid fringe (Mitt Romney’s furious backpedaling after joking, “No one’s ever asked to see my birth certificate”).

Then the nation’s pre-eminent birther ran for president. Trump’s campaign was surreal and an intellectual embarrassment, and political experts of all stripes told us he could never become president. That wasn’t how the story was supposed to end. National Review devoted an issue to writing Trump out of the conservative movement; an editor there, Jonah Goldberg, even became a leader of the “Never Trump” crusade. But Trump won — and conservative intellectuals quickly embraced a man who exploited the same brutish energies that Buckley had supposedly banished, with Goldberg explaining simply that Never Trump “was about the G.O.P. primary and the general election, not the presidency.”

The professional guardians of America’s past, in short, had made a mistake. We advanced a narrative of the American right that was far too constricted to anticipate the rise of a man like Trump. …

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Future historians won’t find all that much of a foundation for Trumpism in the grim essays of William F. Buckley, the scrupulous constitutionalist principles of Barry Goldwater or the bright-eyed optimism of Ronald Reagan. They’ll need instead to study conservative history’s political surrealists and intellectual embarrassments, its con artists and tribunes of white rage. It will not be a pleasant story. But if those historians are to construct new arguments to make sense of Trump, the first step may be to risk being impolite.